1. Field of the Invention
The invention generally relates to valves for pressurized tanks or other pressurized containers, e.g., pressurized gas bottles.
More particularly, a first aspect of the invention relates to valves for pressurized containers which are commercially characterized as being "non-refillable" or "no-return" containers and which, for reasons of safety and otherwise, are not intended for re-use after being "charged" and/or after their initial contents have been emptied. Valves for such containers are also often referred to in the art as "single use" valves for pressurized containers.
A further aspect of the invention relates to blocking elements per se (also sometimes referred to herein as checks or stops) which are suitable for use in non-refillable valves. In particular, blocking elements that are easy to manufacture and install in such valves and which inherently reduce the risk of false check engagement during the valve assembly process (an event that would improperly activate the one way feature of the valve and not allow the container to be initially charged) are the focus of this aspect of the invention.
Yet another aspect of the invention relates to a dual purpose manufacturing process that uses a single basic valve design to enable both refillable and non-refillable valves to be manufactured.
According to this aspect of the invention, the valve design and associated manufacturing process are identical for fabricating the valve housing and fabricating/installing all internal components for both valve types (refillable and non-refillable); except that when using the novel process and valve design to make a non-refillable valve, a blocking element (such as, for example, one of the aforementioned blocking elements which inherently reduce the risk of false check engagement) is inserted into the valve housing as part of the otherwise dual purpose manufacturing process.
Stated another way, the non-refillable valve design contemplated by the aforementioned first aspect of the invention doubles as a good refillable valve structure by merely leaving out the check. This feature enables both refillable and non-refillable valves to be easily mass produced from the same basic design (the single valve design and associated manufacturing process contemplated by this further aspect of the invention) using essentially the same parts list, machine tools, etc.
Still further aspects of the invention are directed toward a valve design (both refillable and non-refillable) that utilizes a mechanically operated primary sealing mechanism (as opposed to valve designs that utilize a pressure differential to open the primary sealing mechanism) to insure seal quality; a valve design that prevents rotation of the primary sealing mechanism in the valve housing to minimize wear, extend valve life and further improve seal quality; a valve design in which the primary sealing mechanism and means for controlling the opening and closing of the valve are optionally made from discrete components formed from differing materials to enable the sealing mechanism to be chemically compatible with the fluid contents of the container even when the controlling mechanism (means for controlling the opening and closing of the valve) is not; and a valve design that is relatively simple and inexpensive, which will allow normal filling of the pressure container under proper conditions, adequate sealing of the pressure during nonuse, selective discharge of the pressure container and, in the case of the non-refillable valves contemplated by the invention, provide effective protection and prevention against improper and unauthorized filling of the container.
2. Description of the Related Art
Pressure tanks or other pressure containers are usually filled under carefully controlled conditions at a charging station and then distributed to other places for use. When empty it is intended that the containers be returned to the charging center for appropriate reuse or destruction in the case of single use containers. Unfortunately, the attractive economies of refilling containers at points of use or otherwise repressurizing them under less than carefully supervised conditions has resulted, in the less consequential cases, in the introduction of impurities or inferior refills and, in the more consequential cases, to injurious explosions. The reuse of pressure containers is highly objectionable for many reasons which relate to safety.
Non-refillable valves are well known in the prior art. Specific examples of known valves include valves of the type described in U.S. Pat. No. 4,543,980, to van der Sanden, issued Oct. 1, 1985; valves of the type described in U.S. Pat. No. 4,573,611, to O'Connor, issued Mar. 4, 1986 (assigned to the same assignee as the present invention), and the various prior art valves described in the aforementioned patents. Both the van der Sanden and O'Connor patents mentioned above are incorporated herein by reference.
In the incorporated van der Sanden patent reference is made to parent applications which illustrate techniques in which one-way ball valves can be used in conjunction with pressurized containers so as to allow for them to be initially charged through an orifice, and wherein further charging is prevented once the initial charge has been completed.
In the parent applications discussed, the prevention of further charging is performed by forcing a ball past a constriction into a final location in a manner such that it cannot return above the restriction. Once the ball is in this final location, it will block any further refilling by simply seating in the valve. However, as noted by van der Sanden, the use of a ball valve is somewhat intricate and complex and requires careful precision machining.
Other non-refillable valve teachings are discussed in van der Sanden, such as the teachings of Walker in U.S. Pat. No. 3,985,332.
Walker discloses a non-refillable safety valve for a pressurized container. The valve includes a housing having a central bore, a hollow knob unit also having a central bore, and a core having a central bore which is slideably mounted in the central bore of the housing. The hollow knob unit is in threaded engagement with the outer wall of the housing. The central bore of the housing provides communication between a port and the pressurized container for charging and selectively discharging of the pressurized container. A sealing member is provided which is slideably mounted in the lower end portion of the central bore of the core. An outwardly biased spring snaps outwardly into a channel to prevent the knob unit from being completely unscrewed. An element prevents the pressurized vessel from being refilled.
When the valve is in the position shown in FIGS. 2-4 or 6 of Walker, refill cannot be accomplished because pressure on the end of central core 220 is greater than the pressure in vessel 100 and thus caused element 132 to seat in the seat in the sealing position. In the position shown in FIG. 1 of Walker, i.e., before spring 216 has snapped into channel 220 as a result of the inward screwing or knob unit 175, element 132 is held away from the seal even if such reverse pressure differential exists. In one embodiment shown in FIGS. 5 and 6 of the Walker patent, a groove 240 is provided in knob unit 176, and outwardly biased unit 216 fits in groove 240 and the adjacent groove formed by rings 208 and 212. In this embodiment, spring 216 prevents removal of knob unit 176: otherwise, operation of the valve system of FIGS. 5 and 6 is essentially the same as that of FIGS. 1-4.
A device such as the one described by Walker is characterized by van der Sanden as being complex and expensive to manufacture.
To address the aforementioned manufacturing problems, van der Sanden describes, in the incorporated patent, a valve for a pressurized container having a blocking element therein which is adapted to occupy an initial location in which fluid can move in and out of the container past the blocking element. According to van der Sanden, the valve and blocking element are further configured such that the blocking element can be irreversibly moved to a position in which the valve permits the escape of fluid under pressure exerted from inside the container, but which automatically closes in response to exposure to an external pressure greater than the pressure inside the container. The blocking element is formed of at least one radially extending arm whose lateral radius is reduced upon movement of the blocking element from the initial location to the final location. The at least one arm expands within the final location to prevent return of the blocking element to the initial location.
The non-refillable valve taught by van der Sanden, although offering manufacturing advantages over the prior art valve designs known at that time, still requires the use of a complex and relatively costly manufacturing process, for specific reasons described immediately hereinafter; and suffers from certain performance limitations as well, also described immediately hereinafter.
In particular, the valve housing described by van der Sanden requires the formation of manufactured undercuts or "blinds" in order to function properly. For example, the undercut shown at location 37 in FIG. 1 of the incorporated patent to van der Sanden (where the central core of the valve shown in FIG. 1 is wider immediately below location 37 than it is immediately above that location), is a requirement for practicing the referenced invention and adds complexity and expense to the valve housing manufacturing process.
Furthermore, according to van der Sanden's teachings, the blocking element is "directional", that is, it needs to be carefully inserted in the proper direction during the manufacturing process for the valve to work at all.
Further still, the valve taught by van der Sanden requires the blocking element, in all of the various embodiments set forth in the reference, be held in its initial position (to facilitate initial charging of the container), by a connection of the blocking element to a stem, rod or some other valve component; or makes the operation of the blocking element dependent on the proper operation of another movable internal valve component, such as a slideable rod, etc., for its proper positioning. Steps such as these further complicate the valve manufacturing process. Operationally, this requirement also introduces a potential performance limitation affecting valve reliability since blocking element linkage with or dependency on other valve components becomes a factor in achieving valve reliability.
A blocking element that does not need to be connected to a stem, rod or some other internal valve component; or otherwise depend on the operation of another movable internal valve component, such as a slideable rod, etc., for its proper positioning, is defined herein to be a "freestanding" blocking element (or check).
Still further, by using the type of blocking device specifically called for by van der Sanden (having at least one flexible, radially extending arm, without further limitation), the referenced valve runs the risk of having its one way feature inadvertently activated during assembly, i.e., causing a false engagement of the blocking device during the valve assembly process. This undesirable result can occur if the blocking element traverses too far down the central bore of the valve during the assembly process (typically involving the insertion of other valve components on top of the blocking element or screwing in of a valve control mechanism to which the blocking element is attached, etc.). Such an event may occur in a valve like van der Sanden's that features a flexible blocking element having radially expanding arms as a main attribute. The use of such arms, without further structural limitations, teaches away from providing a sufficiently rigid blocking element having the structural integrity to, for example, prevent an arm from snapping off under mechanical pressure, or for preventing the passage of the blocking element past a predetermined point without the exertion of a predetermined amount of driving force, etc.
With respect to the incorporated O'Connor patent, a non-refillable valve which differs in many important respects from the teachings of van der Sanden is described. For example, the O'Connor valve uses pressure instead of a mechanical force to release the primary valve seal; O'Connor utilizes the same element for making a primary valve seal when closing the valve as is used (i.e., the element doubles as) the blocking element, etc. However, many of the same problems inherent in manufacturing a non-refillable valve are common to both van der Sanden's teachings and those of O'Connor such as, for example, the requirement that the valve housing used have manufactured undercuts, the blocking element used is still "directional", i.e., it needs to be carefully inserted in the proper direction during the manufacturing process for the valve to work, the blocking element is not "freestanding", as defined hereinabove, etc.
Still other problems related to prior art valve designs, blocking elements used in non-refillable valves and the known valve manufacturing processes themselves, exist.
Examples stated in terms of the needs that result from such problems include: (a) the need for a dual purpose manufacturing process that uses a single basic valve design to enable both refillable and non-refillable valves to be manufactured using essentially the same parts list, machine tools, etc.; instead of the present practice of having to execute dedicated manufacturing process for producing refillable versus non-refillable type valves (because of differing housing types that are used, different components required for valve operation, etc.); (b) the need for a valve design (both refillable and non-refillable) that utilizes a mechanically operated primary sealing mechanism (as opposed to valve designs that utilize a pressure differential to open the primary sealing mechanism) to insure seal quality while solving the other problems with known valves indicated hereinabove; (c) the need for a valve design that prevents rotation of the primary sealing mechanism in the valve housing to minimize wear, extend valve life and further improve seal quality; (d) the need for a valve design in which the primary sealing mechanism and means for controlling the opening and closing of the valve are optionally made from discrete components formed from different materials to enable the sealing mechanism to be chemically compatible with the fluid contents of the container even when the controlling mechanism (means for controlling the opening and closing of the valve) is not; and (e) the need for a valve design, solving all of the aforementioned problems and meeting the aforestated needs, which is relatively simple and inexpensive, which will allow normal filling of the pressure container under proper conditions, adequate sealing of the pressure during nonuse, selective discharge of the pressure container and, in the case of the non-refillable valves contemplated by the invention, provide effective protection and prevention against improper and unauthorized filling of the container.
Accordingly, for all of the reasons stated hereinbefore, it would be desirable if methods and apparatus relating to valves for pressurized containers were available for providing (a) valves having a "unidirectional stepped" valve housing, defined herein as a valve housing that includes a central bore having two or more stepped portions each radially increasing (or conversely decreasing) as the bore is traversed in a given direction. A unidirectional stepped valve housing would not require manufactured undercuts or inserted components to properly function; as opposed to prior art valve designs (exemplified hereinbefore with reference to the incorporated patents) which require the formation of "blinds", etc.; (b) non-refillable valves which include a "reversible check" (a blocking element), i.e. a check that can be installed in the aforementioned valve housing in either of two directions for proper valve operation; as opposed to prior art non-refillable valves that utilize directional checks (it should be noted that a symmetrical reversible check would be even more desirable to further simplify the manufacturing and installation process and accordingly is preferred); (c) non-refillable valves which include a "freestanding" check (as defined hereinbefore) to simplify the valve manufacturing process further (by eliminating assembly steps), enhance valve reliability (by minimizing the number of required actions for the valve to work), lower valve and check manufacturing costs, etc.; and (d) non-refillable valves which include a check that integrally incorporates a "deformable" member (blocking element, check, stop means, etc.), as defined hereinafter, which automatically operates to prevent the return of the check to an initial location upon movement of the blocking element from the initial location to a final location (thereby activating the one way feature of the valve); and which is designed to inherently reduce the risk of false check engagement during the valve assembly process, an event that would improperly activate the one way feature of the valve and not allow the container to be initially charged.
A "deformable" member (blocking element, check, stop means, etc.) is defined herein as a member which changes shape under the influence of a predetermined amount of force required to drive the member through an opening; but which is relatively rigid when not under the influence of the predetermined amount of force in order to withstand the premature forcing of the member through the opening. Such member would also preferably possess a predefined degree of structural integrity that in addition to inhibiting false engagement, tends to prevent pieces of the member from breaking when the member is being driven or otherwise forced through the opening.
Furthermore, it would be desirable to provide: (a) blocking elements (checks) per se, for use in non-refillable valves, which are easy to manufacture and install, which inherently reduce the risk of false check engagement during the valve assembly process, and possess the other characteristics of desirable checks referred to hereinabove (such as being reversible, symmetrical, etc.); (b) a dual purpose manufacturing process of the type referred to hereinabove, for manufacturing both refillable and non-refillable valves; (c) a valve design that utilizes a mechanically operated primary sealing mechanism to insure seal quality and prevents rotation of the primary sealing mechanism in the valve housing to minimize wear, extend valve life and further improve seal quality to meet the need for these features set forth hereinbefore; (d) a valve design in which the primary sealing mechanism and means for controlling the opening and closing of the valve are optionally made from discrete components for the reasons stated hereinbefore; and (e) a valve design that incorporates the other desirable features set forth hereinabove and yet remains relatively simple and is inexpensive to produce.